This invention relates in general to slip joints, such as are commonly used in vehicle drive train systems, for transmitting rotational force or torque between telescoping members, while accommodating a limited amount of relative axial movement therebetween. In particular, this invention relates to an improved structure for a splined member that is adapted for use in such a slip joint.
In a typical land vehicle, a drive train system is provided for transmitting rotational power from an engine/transmission assembly to an axle assembly so as to rotatably drive one or more wheels of the vehicle. A typical drive train system includes a driveshaft assembly that is connected between an output shaft of the engine/transmission assembly and an input shaft of the axle assembly. To accomplish this, a first universal joint is connected between the output shaft of the engine/transmission assembly and a first end of the driveshaft assembly, while a second universal joint is connected between a second end of the driveshaft assembly and the input shaft of the axle assembly. The universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft assembly to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes thereof.
Not only must the drive train system accommodate a limited amount of angular misalignment between the engine/transmission assembly and the axle assembly, but it must also typically accommodate a limited amount of relative axial movement therebetween. A small amount of such relative axial movement frequently occurs when the vehicle is operated. To address this, it is known to provide a slip joint in the driveshaft assembly of the drive train system. A typical slip joint includes male and female telescoping members having respective pluralities of splines formed thereon. The male splined member has a plurality of outwardly extending splines formed on the outer surface thereof that cooperate with a plurality of inwardly extending splines formed on the inner surface of the female splined member. The cooperating splines of the male and female members provide a rotational driving connection through the slip joint, while permitting a limited amount of relative axial movement therebetween. The slip joint may be provided at the ends of the driveshaft assembly or in the interior thereof, as desired.
Conventional splined members are often formed by a machining process, wherein material is removed from a member to form splines therein. To accomplish this, the member is initially formed having a surface of predetermined size and shape. Then, a cutting tool (such as a hobbing tool) is moved into engagement with the surface of the member to remove some of the material therefrom. The material that remains on the member becomes the plurality of splines. As a result of this machining process, the splines are usually formed having relatively square faces, i.e., faces that are generally flat and extend generally radially relative to the rotational axis of the member. Then, the splined member is coated with a material having a relatively low coefficient of friction. The low friction coating is provided to minimize the amount of force that is required to effect relative movement between the two splined members. Also, the low friction coating provides a relatively tight fit between the cooperating splines of the two splined members, thus minimizing any undesirable looseness therebetween while continuing to allow free axial movement.
Although the above-described machining process for forming splines has functioned satisfactorily for many years, it has been found to be somewhat inefficient. This is because the machining process has been found to be relatively slow and expensive to perform. Also, the machining process results in a quantity of scrap material of which must be disposed. Thus, it would be desirable to provide an improved structure for a splined member for use in a slip joint and an improved method for manufacturing the same.
This invention relates to an improved structure and method for manufacturing a splined member for use in a slip joint for transmitting rotational force between two members, while accommodating a limited amount of relative axial movement therebetween. The splined member can include a female tubular member having an inner surface provided with a plurality of longitudinally extending grooves that are sized and spaced in accordance with a desired number and position of splines to be formed. A elongated rod is disposed in each of the longitudinally extending grooves formed in the inner surface of the female tubular member. A quantity of positioning material is provided within spaces provided between the elongated rods and the longitudinally extending grooves. The positioning material is then hardened to support the elongated rods in the longitudinally extending grooves to define a plurality of inwardly extending splines in the female splined member.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.